Reducing fouling in refining of petroleum products by salicylidene additive



United States Patent O REDUCING FOULHNG IN REFINKNG F PETRO- LEUM PRODUCTS BY SALICYLHDENE ADDITEVE Richard M. Miller, La Grange, ill., assignor to Nalco Chemical Company, Chicago, Ill., a corporation of Delaware No Drawing. Continuation of application Ser. No. 373,041, June 5, 1964. This application July 17, 1967, Ser. No. 653,610

Int. Cl. Cg 9/16 US. Cl. 208-48 16 Claims ABSTRACT OF THE DlISCLOSURE RELATED APPLICATION This application is a continuation of my copending application Ser. No. 373,041, filed June 5, 1964, now abandoned.

BACKGROUND OF THE INVENTION It is common practice to add chemical agents to finished petroleum hydrocarbon products such as gasolines, kerosenes, fuel oils, finished solvents, and the like, to give these products desirable properties and characteristics. Modern processing operations use a large number of hydrocarbon charge stocks which are intermediates in the production of finished products. Until recently little attention was paid to the properties of these charge stocks since they were rapidly processed through processing equipment where they were converted to products having different physical and chemical characteristics from those of the starting material.

With the commercial growth of the petrochemical industry and the ever-increasing need for higher octane gasolines, improved aviation fuels and improved residual fuels, it has become the practice to treat the various refinery charge stocks to extract improved fuel values therefrom or to convert them to valuable petrochemicals.

These various processes have tended to increase processing problems which, in the past, were not so critical.

One of the worst problems encountered in the treatment of various hydrocarbon charge stocks is the phenomenon which is now recognized and is descriptively called fouling. This phenomenon manifests itself in the form of deposits which frequently form on the metal surfaces of the processing equipment and tend to materially decrease the efiiciency of the intermediate processing operations. The direct results of fouling appear in the fonns of heat transfer loss, increased pressure drops, loss in throughput and, in some instances, a specific type of corrosion product which is associated with the deposits.

The charge stocks which most commonly cause fouling in the intermediate refinery equipment are naphthas, gas oils, crudes, and petroleum gases. The naphthas or light distillate stocks may be considered as a light oil and usually have boiling point range of 90500 F. The gas oils are intermediates between the so-called kerosene fractions and the light lubricating cuts, and generally distill from 520 F. and 750 F. These gas oils are usually used as charges to cracking units where the molecules are broken down into smaller components. The crude oils 3,492,219 Patented Jan. 27, 1970 "ice which most commonly cause the problem of fouling are virgin products charged to the first refining stage operations and contain all of the petroleum fractions normally removed in the refining processes. For the purposes f this invention, crude stocks are intended to cover the so-called residual or pot fractions which remain after the volatile components and solvent extractable components of the crudes have been removed.

Another class of hydrocarbons to which the invention pertains is the petroleum gases or normally gaseous, alkane and alkene hydrocarbons, which usually boil between -250 F. and F., i.e., methane, ethane, propane, butane, ethylene, propylene, etc. These hydrocarbons may be in the liquefied state or gaseous state during processing thereof in the practice of the invention. For example, these normally gaseous stocks may become liquefied when subjected to super-atmospheric pressures or low temperatures.

The various charge stocks mentioned above are most frequently subjected to one or more of the following general type thermal or catalytic processes to produce fuels: reforming, cracking, alkylation, isomerization, polymerization, desulfurization, hydrogenation, and de hydrogenation. A description of these various processes and their modifications are described in the publication, Petroleum Refiner, September 1962.

Similar roblems arise in equipment used in the petrochemical industry wherein the hydrocarbon charge stock is, in many cases, heated at normal or elevated pressure. For example, in the production of acetylene by the BASF process, light napthas or natural gas is preheated prior to partial combustion thereof with oxygen to form acetylene and other by-products. In other acetylene production processes, hydrocarbons such as naphthas are cracked thermally. In the alkylation of aromatics, benzene or other aromatic hydrocarbon is mixed with an olefin-containing gas, preheated to the alkylation temperature, and reacted in the reactors. Ammonia is produced by processes involving a first stage comprising mixing a compressed hydrocarbon gas, liquid hydrocarbon, or the like, with steam, preheating the mixture and forming in a reactor a gas product composed primarily of carbon monoxide and hydrogen, the latter being reacted with nitrogen at a later processing stage. Benzene and hydrogen are reacted in equipment utilizing heat exchangers to produce cyclohex-ane. Light alkane hydrocarbons, mono-olefins and mixtures thereof are preheated before catalytic dehydrogenation into mono-olefins and di-olefins. Ethylene feed is preheated under pressure before reaction with water to produce ethanol. Light and heavy crude oil or crude oil fractions as well as light hydrocarbon gasses are preheated before thermal cracking therof into ethylene and propylene and C olefins. In the hydrodealkylation of lower alkyl aromatics into simple aromatics and gas, the lower alkyl aromatics are mixed with hydrogen and preheated before the hydrodealkylation reaction.

The foregoing examples of petrochemical processes are illustrative but not exhaustive of processes in which the invention may be used to advantage in reducing deposit formation on heat exchange surfaces by hydrocarbons employed therein. Other petrochemical processes to which the invention applies may be found in the Petrochemical Handbook Issues of the Hydrocarbon Processing and Petroleum Refiner, the latest issue of which appears at pages 129 if. of vol. 42, No. 11, November 1963 (Gulf Publishing Co.).

The deposits previously mentioned most frequently occur on heat exchange surfaces at elevated temperatures which range between 100 F. and 2000 F. and more often between 200 F. and 2000 F. The types of mechanical equipment most commonly affected are furnaces, heat & exchangers, reboilers, condensers, compressors and auxiliary equipment. Catalyst beds may also become severely fouled by these deposits. In the mechanical types of equipment, the charge stock is usually caused to flow through various types of heat processing equipment such as pipes,

heat exchangers, furnaces, etc., which, for purposes of simplification, are referred to herein as conductors.

The deposits forming on the heat exchange surfaces such as metal surfaces are varied in composition and may be either organic, inorganic, or mixed organic and inorganic. The organic deposits are primarily polymerization products and are usually black, gummy masses which may be converted to coke-like masses at elevated temperatures. The inorganic portions of the deposits will frequently contain such components as silica, iron oxide, sulfur trioxide, iron sulfide, calcium oxide, magnesium oxide, inorganic chloride salts, sodium oxide, alumina, sodium sulfate, copper oxides, and copper salts. The source of the inorganic components of the deposits is difficult to locate in any one given operation, but frequently they may be ascribed as coming from such sources as ash components of the crude oils, corrosion products from the metal surfaces which the charge stocks contact, and contaminants resulting from the contact with the various metallic catalytic reagents used to process the stock.

The problems described above are distinguishable from the prior art phenomena of corrosion and sludge formation which frequently occur in finished products. The

problem of sludge or deposit formation in finished products is not related to that of fouling since deposits of the former type may be readily solubilized using such organic solvents as benzene, acetone, and the like. The deposits which are referred to herein as fouling are not readily solubilized by common organic solvents. The inorganic deposits which occur as fouling products are frequently much more complex in their make-up than the conventional corrosion products; hence they are readily distinguishable on this basis.

When the fouling phenomenon first became apparent, it was believed it could be corrected by using known antioxidants or stabilizing chemicals to mitigate the problem. The experience with these additives soon developed the fact that conventional petroleum additives were relatively ineffective.

It would be a valuable contribution to the art if the problems described above could be overcome by using economical chemical additives at relatively low dosages. This invention presents such a solution to the problem.

The invention in its simplest form comprises a pctroleum refining process for the production of liquid and gaseous hydrocarbons or hydrocarbon processing processes for production of petrochemical products and hydrocarbon products wherein a hydrocarbon charge stock contacts a heat exchange surface such as a metal conductor under conditions of temperature and pressure which cause the formation of deposits on the surfaces of the heat exchanger. To prevent the formation of these deposits or fouling, the process is performed in the presence of a chemical additive which is admixed with the charge stock. The chemicals capable of preventing the fouling are oil soluble metal deactivators.

The mechanisms of fouling of heat exchange surfaces must be evaluated in the light of the feed stock. In the distillation range of approximately ZOO-400 F a variety of compounds from crude oil distillation can exist. The addition of cracked stocks to straight run naphtha stream and the oxidation of these naphthas in storage add other hydrocarbon and nonhydrocarbon compounds. For the purpose of discussing fouling mechanisms, these compounds will be considered individually according to classification.

Parafi'inic compounds may be straight chain or branched hydrocarbons. Generally, they are relatively stable to oxidation at elevated temperatures. It has been reported that oxygenated products are produced in the vapo g ee; react on of paralfine with O yg n t 70 to peroxides and dihydroperoxides. Other investigators have shown that these hydroperoxides are able to condense and from polymeric materials and Water Evaluations have shown that straight run naphthas containing no measurable olefins, hydrogen sulfide, mercaptans, or dissolved oxygen do not form more than trace amounts of deposit in the heat exchangers unless the bulk oil temperature exceeds approximately 750 F. At this temperature and above, thermal cracking of the paraffin occurs, producing compounds which can react to form polymeric deposits. As Will be discussed later, metallic catalysts may participate in the reaction.

Monoand bicycloparafiin have been reported in the gasoline fraction of crude oil. The monocycloparaffins' consist mostly of cyclopentanes and hexanes with minute amounts of cycloheptane. The bicycloparaffins may consist of methyl-(2.2.1) bicycloheptane, bis-bicyclo-(3.3.0) octane, Tetralin and Decalin. Little is known of the thermal stability of the first two of these compounds, but their decomposition would probably be similar to that of the normal paraffins. Tetralin and Decalin enter into dehydrogenation reactions at elevated temperatures. If benzene is the final product, a more thermally stable compound is produced with the balance consisting of unsaturates.

With refiners reaching deeper into the crude barrel to produce more gasoline, it is not surprising that the products of thermal and catalytic cracking of heavier fractions currently contribute up to twenty-five percent of the feed to hydrodesulfurizers and reformers. The primary useful product of cracking prodcesses is a naphtha high in olefin content plus sulfur, nitrogen, and oxygen compounds. Theconjugated olefin content may be as high as five percent. In many cases gum formers in coker 'distillates have been found to be these conjugated olefins.

That olefins are capable of intrareacting to produce polymeric compounds, is well known. They are also able to react, via metal catalysts, with oxygen, oxygen organo-sulfur compounds, and oxygen-organo-nitrogen compounds.

The oxygen-olefin reaction, in the presence of metal catalyst, has been reported by several investigators. The primary reaction product is a peroxide. It has been proposed that the metal at an oxiation state of plus two, is capable of extracting hydrogen from an olefin, producing a free radical. This free radical reacts with an oxygen molecule to produce a peroxide. The peroxide free radical reaction products may rearrange, losing water, to form a variety of aldehydes, ketones, acids and esters. Some of these, in turn, are able to react with other components in the feed stock, producing polymeric substances. These reactions will be considered in greater detail below.

Laboratory evaluations have shown that naphthas containing cracked stocks, or the cracked stocks by themselves, have markedly higher fouling rates and give greater tube deposit ratings than straight run stocks. Evaluations of naphthas from field units have shown that oxygen exists even in nitrogen blanketed naphtha feed stocks. This effect of dissolved oxygen is used in laboratory fouling evaluations to increase the fouling rate, and thus shorten the length of each test, via pre and continued saturation of the feeds with air.

The sulfur content of straight run naphthas may range from 0.01-0.17 percent. In the cracked naphthas it may be as high as 0.5 percent. The sulfur compounds in these naphthas consist of thiols (mercaptans), heterocyclics, sulfides, and polysulfides and thioethers.

It has been reported that mercaptans are capable of interreacting to form olefins and hydrogen sulfide. The mechanism involves the decomposition of the mercaptan to a f ee radical. This rad c l then unde goes an intra= molecular splitting which results in the olefin and hydrogen sulfide. The reactions at 750 F., produced considerable olefin and hydrogen sulfide. At lower temperatures, this reaction was not pronounced.

Sulfur compounds are also capable of reacting with olefins producing polymeric compounds. Authors have reported the reaction of olefins with mercaptans in the presence of oxygen to produce a substituted 2-hydroxyethyl sulfoxide.

A wide variety of nitrogen compounds have been found in crude oil. Straight run naphthas obtained from high nitrogen crudes may contain some of the lower molecular weight cyclic or heterocyclic nitrogen compounds. Another source of nitrogen compounds in reforming feed stocks is cracked naphtha. Cracked naphthas containing high nitrogen contents are usually highly colored and exhibit high fouling rates both in the field and in laboratory evaluations.

Refinery naphtha streams usually contain trace amounts of dissolved or suspended metal salts, primarily as a result of corrosion reactions. Evaluations indicate that not only copper, but others such as iron, nickel, and chromium may augment deposit formation.

Thus far only possible chemical reactions in the formation of exchanger deposits have been considered. These reactions are most probably affected by temperature, pressure, mass flow rate, residence time, and the physical condition of the reactor, in this case the exchanger tube.

It has been found that increased temperature, and residence time generally increase the fouling rate. Flow rates are dependent upon pressure and the volatility of the feed stock. When a feed stock is vaporized, the heat flux is higher, to obtain a specific temperature, than when no vaporization occurs. Thus, the skin temperature of the exchanger tube is higher, so that increased cracking and coking occurs. However, the increased velocity of the naphtha as a gas tends to sweep the surface, removing a portion of the coke, sometimes giving the appearance of a lower fouling rate. In this area, the type of coke formed may not lend itself to this sweeping and velocity will have little effect.

To summarize briefly reactive olefins in the feed stock are probably capable of forming free radicals via trace metal catalysts, which then react with oxygen to produce peroxides. These peroxides probably react with themselves, sulfur and/or nitrogen compounds producing polymeric substances. These polymeric surfaces of the exchanger tube and to corrosion products present in the feed stock. Subsequent reactions take place at the exchanger surface which transform the gum deposit to coke dispersed with corrosion product.

DESCRIPTION OF THE INVENTION This invention is a departure from the dispersant theory for reducing fouling of hot, heat exchange surfaces. It has been discovered that fouling of hot surfaces of heat exchange tubes, catalyst beds and the like in direct contact with liquids or vapors of gas oils, lower alkanes, lower alkenes, aromatics, naphthas and crude oils in hydrocarbon processing operations can, in many cases, be considerably improved at materially lower dosages than the commercially-used, dispersant antifoulants by dispersing or dissolving in a refinery petroleum stock of the aforesaid character a deactivator for a metal such as copper, chromium, nickel, iron and/or manganese in a small but sufiicient amount to reactivate by complexing the small amounts of these metals in the particular feed stock. By deactivating metals which catalyze the formation of fouling deposits, the fouling problems on hot, heat exchange surfaces in direct contact with the liquid feed stock or vapors thereof diminish appreciably even to the extent that dispersant-type antifoulant treatment may be completely replaced by the deactivator treatment.

The metal deactivators are added to and dispersed in the stock of the aforesaid character prior to contact of the stock with the hot, heat exchange surface whereby sufficient deactivation of the metals carried in the stocks will reduce fouling. These metals are generally present in amounts of about 0.1-500 p.p.m., based on the weight of the stock. The stock-contacting surface of the heat exchanger is hotter in a flow type heat exchanger than the temperature of the stock, the former temperature being in the order of 200'2000 P. The preferred metal deactivator may be one of several types, some of which are known and used to stabilize gasolines and the like against oxidative deterioration during storage.

One preferred class of metal deactivators is prepared by the condensation of two mols of a hydroxy-benzaldehyde with one mol of an aliphatic or aromatic diamine and has the general formula wherein R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a ring carbon atom ortho to the CH=N group, and R represents a group of the class consisting of aromatic groups, cycloaliphatic groups containing 6 carbon atoms in the ring, and heterocyclic groups containing heterocyclic rings of 6 atoms, the hetero atom being nitrogen, and in which the two N atoms are attached directly to adjacent ring carbon atoms or to the most closely positioned ring carbon atoms of different rings other than carbon atoms forming part of the linkage between the two rings of the R group and an aliphatic radical having the two N atoms attached directly to different carbon atoms of the same open chain of R.

Compounds of the aforesaid structure with an unsaturated hydrocarbon side chain may also be used. The deactivator in this case comprises an N,N' di (3 alkenylsalicylidene) diaminoalkane. A particularly preferred metal deactivator comprises N, N di (3 allylsalicylidene) 1,2 diaminopropane which is prepared by the condensation of 2 mols of allylsalicylaldehyde with 1 mol of 1,2 diaminopropane. Other metal deactivators include N,N' di (3 methallylsalicylidene) 1,2 diaminopropane, N,N di (3 crotylsalicylidene) 1,2 diaminopropane, N,N' di[3 (2 pentenyl)salicylidene] 1,2 diaminopropane, N,N' di[3 (2 hexenyl)salicylidene]- 1,2 diaminopropane, N,N di[3 (2 heptenyl)salicylidene] 1,2 diaminopropane, N,N' di [3 (3 methyl 2 butenyl)salicylidene]1,2 diaminopropane, etc.

While 1,2 diaminopropane preferably is used for condensation with the allylsalicylaldehyde compound in preparing the metal deactivator, other suitable diaminoalkanes may be employed. Illustrative diaminoalkanes include 1,2 diaminoethane., 1,3 diaminopropane, 1,2 diaminobutane, 1,3 diaminobutane, 1,4 diaminobutane, 1,2 diaminopentane, 1,3 diaminopentane, 1,4 diaminopentane, 1,2 diaminohexane, 1,3 diaminohexane, 1,4 diaminohexane, etc. When using these diaminoal kanes the metal deactivator compound will be similar to the specific compounds hereinbefore set forth except for the diaminoalkane grouping. For example, when condensing 1,2 di aminoethane with 3 allylsalicylaldehyde, the metal deactivator will be N,N' di (3 allylsalicylidene) 1,2 diaminoethane. Similarly when condensing 1,2 diaminobutane with 3 allylsalicylaldehyde,

the metal deactivator will be N,N' di (3 allylsalicylidene) 1,2 diaminobutane, etc.

While it is preferred that allylsalicylaldehyde or other salicylaldehyde compounds having a side chain containing an allyl group be used in preparing the metal deactivator, in another embodiment the unsaturation may be in the alpha or other position other than alpha (i.e., beta). Illustrative compounds having an alpha unsaturation include N,N' di (3 vinylsalicylidene) 1,2- diaminopropane, N,N di (3 isocrotylsalicylidene) 1,2 diaminopropane, etc. Illustrative compounds having the unsaturation in a different position include N,N di- [3 (3 butenyl)salicylidene] 1,2 diaminopropane, N,N' di [3 (3 pentenyl)salicylidene] 1,2 diam ino propane, N,N di [3 (4 pentenyl)salicylider1e]- 1,2 diarninopropane, etc.

Another class of metal deactivators are o-hydroxyarylamides of o-hydroxyl aryl carboxylic acids having the structure 2 wherein R and R represent hydrogen, alkyl, alkoxy or halogen and may be the same or ditferent. Among the compounds of the invention 2,2 dihydroxy benzanilide has been found to be particularly effective for the achievement of the objects of the invention.

Other arylamides within the scope of the invention are dihydroxy-dialkyl-benzanilides such as 2,2-dihydroxy- 3,3 dimethyl benzanilide; 2,2 dihydroxy-3,3-diethyl benzanilide; 2,2 dihydroxy 4,4-dimethyl benzanalide; 2,2 dihydroxy 5,5-di-isopropyl benzanilide; 2,2-dihydroxy 4 methyl-6-amyl benzanilide; 2,2-dihydroxy- 5,5'-diethyl benzanilide; 2,2'-hydroxy-6,6-dimethyl-benzanilide; 2,2-dihydroXy4-ethyl-6'-amyl benzanilide; 2,2- dihydroxy 4 isopropyl-6-butyl benzanilide; 2,2-dillydroxy-3-methyl-4--methyl benzanilide; 2,2-dihyd1'oxy-4- ethyl-6-methyl benzanilide, and equivalent compounds, particularly wherein the alkyl substituents are alkyl radicals of one to six carbon atoms.

Also useful as metal deactivators in accordance with the invention are dialkoxy substituted 2,2-dihydroxy benzanilide such as 2,2 dihydroxy 3,3 dimethoxy benzanilide; 2,2 dihydroxy 3,3'-diethoXy-benzanilide; 2,2- dihydroxy 4,4 diethoxy benzanilide; 2,2-dihydroxy-4- propoxy 6' butoxy benzanilide; 2,2'-dihydroxy-5,5'-diethoxy benzanilide; 2,2 dihydroxy 6,6 dimethoxy benzanilide; 2,2'-dihydroxy-4-methoXy-6-butoxy benzanilide, 2,2-dihydroxy-3-methoxy-5'-methoxy benzanilide; 2,2 dihydroxy 4 ethoXy-6-methoxy-benzanilide and similar compounds which are disubstituted with the same or different alkoxy radicals, particularly with alkoxy radicals containing from one to six carbon atoms.

Also useful as metal deactivators in organic compositions are dihalo 2,2-dihydroxy benzanilides, such as 2,2- dihydroxy-3,3'-dibromo benzanilide; 2,2'-dihydroxy-4,4- dichloro-benzanilide; 2,2'-dihydroxy-5,5-difluoro-benzanilide; 2,2 dihydroxy 6,6-diiodobenzanilide; 2,2-dihydroxy 3 chloro-5'-chloro benzanilide; 2,2-dihydroxy-3- bromo-3'-chloro benzanilide; 2,2'-dihydroxy-4-fluoro-6- iodo 'benzanilide and equivalent dihalo compounds.

In addition to the foregoing compounds wherein the mono-substituent of each benzene ring is selected from the same general group of atoms or radicals, i.e., hydrogen, alkyl, alkoxy or halogen, compounds in which each benzene ring is substituted with radicals or atoms selected from different groups may also be utilized. Mixed compounds typical of the group are alkyl-alkoxy, alkyl-halo and alkoxy-halo 2,2-dihydroxy benzanilides wherein the mixed substituents are located either symmetrically or asymmetrically at the 3, 4, 5 or 6 positions of the two benzene rings.

Another class of metal deactivators is prepared by the reaction of N,N-dialkenylmelamine with a salicylald-chyde. A particularly preferred N,N-dialkenylmelamine for use in the present invention is N,N-diallylmelamine. The preparation of this type of composition of the present invention is illustrated by the reaction of N,N-diallylmelamine and salicylaldehyde, with the understanding that these re c ions a e ypical and th t other N,N-dial ylmelamines and substituted salicylaldehydes may be used. The compounds have the following general structures:

alkenyl-N-alkenyl and wherein R is selected from the group consisting of hydrogen and a hydrocarbon radical.

Still another class of metal deactivators comprises those of the general structure R! 7 II HO-R- NNII(,NH-R

wherein R represents an ortho-divalent radical, aromatic in nature, R represents a member selected from hydrogen and hydrocarbon radicals, R represents a member selected from hydrogen and organic radicals and X represents a member selected from :0, :S and :NH.

Preferably, R in the formula represents an ortho-divalent aromatic radical of the henzene series, that is, contains only one benzene ring. A preferred class of compounds are the l-(ortho-hydroxy arylidene) aminoguanidines, particularly those in which the arylidene group is of the benzene series. The simplest and preferred member of this group is l-salicylalaminoguanidine.

Another subgenus of the above are the l-(orthohydroxy arylidene) semicarbazides. iln this case also the arylidene group is preferably of the benzene series. The simplest and preferred member of this case is l-salicylalsemicarbazide which has the formula The third group of compounds of our invention consists of the 1 (ortho hydroxy arylidene) thiosemicarbazides of which the simplest member is 1-salicylalthiosemicarbazide having the formula Besides many others, the following compounds are metal deactivators within the scope of our invention:

1-(2'-hydroxy-3-methoxybenzal) semicarbazide 1-( 2'-hydroXy-5'-ter-butylbenza1) semicarbazide 1- 2-hydroxy-5 -methylbenzal) thiosemicarbazide l-(2-hydroxy-3-chl0r0benzal) aminoguanidine 1-(2-hydroxypropiophenone) semicarbazide 1- 2'-hydroxy-5 '-methylacetophenone) thiosemicarbazide 1 2'-hydroxybenzal) -4-isobutylaminoguanidine 1 (2' hydroxy 5' ter-butylacetophenone) thiosemicarbazide 1- Z'-hydroxyacetophenone -4-methylsemicarbazide 1 (2' hydroxybenzophenone) 4 isopropylthiosemicarbazide The most preferred deactivators are those of the formula a -OH HO wherein R is hydrogen or an alkyl group of 116 carbons, preferably hydrogen or alkyl of 1-4 carbons, as in N,N-disalicylidene-ethylene diamine or N,N'-disalicylidene-1,2-propane diamine and the like.

The metal deactivators in general are somewhat corrosive, especially toward metal reaction vessels during preparation thereof, and it is, accordingly, often advantageous to employ a compatible corrosion inhibitor to minimize corrosion of the reaction vessel. Also, the corrosion inhibitor can be of benefit in lessening corrosion of the hot, metal, heating surfaces.

The deactivators are used as dosage ranges from as little as one part per million to dosages ranging as high as 500 parts per million. The benefits of the invention can be realized even in cases wherein the amount of metal deactivator is less than the theoretical stoichiometric quantity for complexing all of the metal contaminants in the hydrocarbon, e.t., about 50% or more of the theoretical stoichiometric quantity. The optimum treatment level which will work is dependent upon the type of charge stock, the type of operation which the stock is subjected, and the temperature to which the particular hydrocarbon is heated. As a general rule, the dosage range for crudes will be between 1 part per million and 300 parts per million and preferably 5-200 parts per million. In the case of naphthas, the dosage range Will be between 1 part per million and 200 parts per million with a preferred treating range being at between 5 and 100 parts per million. When gas oils are treated, the dosage may vary from 1 part per million to 300 parts per million, with optimum dosage levels being between 5 and 100 parts per million. In the case of petroleum gases optimum dosage levels are between 1 and 200' parts per million and more often 5-100 parts per million.

One of the most interesting features of the invention is that the additive remains preferentially with the liquid phase of the charge stock during the various refining stages. Thus, for instance, if a gas oil is subjected to a catalytic process, the additive does not carry over to any appreciable extent into the finished product, but will remain behind with the residual and nonconverted components of the liquid or be catalytically destroyed.

The additives may be added to the charge stock at any point in the process to be protected and will carry along with the production until such a point in the refining operation where the product is converted into a different chemical component or species.

Thus, where a crude stock is passed through heat exchangers to a thermal distillation unit to remove the lighter fractions, the additive may be added just prior to the heat exchanger section of the operation and will afford protection to both the exchanger surface and other surfaces of the distillation or fractionation unit.

By indicating that the surfaces of the various units are protected, it is meant that the charge stock has been rendered nonfouling as to the heat exchange surfaces such as metal surfaces; hence, deposit build-up does not occur. The process may, therefore, be considered as preventative rather than corrective in its operation. In some cases, the additives will remove existing fouling, but in most instances, the function of the additives is to prevent fouling rather than remove existing deposits.

The invention and its advantages will be further appreciated from the following specific examples thereof, which are provided as preferred embodiments of the generic invention. The parts and percentages are by weight unless otherwise specified.

The laboratory unit employed to evaluate antifouling properties of various compositions consisted of a feed tank, a waste tank, a nitrogen pressurizing system, a valve and rotameter to control the bleed-off of nitrogen from the waste tank, valves to control the flow of feed stock from the fuel tank to the heater section and the waste tank, and a heater section which consists of an annular heat exchanger through which the feed stock flows and is heated to field process temperatures. Flow from the feed tank to the waste tank by way of the heat exchanger is accomplished by maintaining the pressure in the waste tank lower than that of the feed tank.

A feed stock entering at the bottom of the exchanger system is at room temperature and the desired pressure. As the feed travels up the exchanger, it is heated to temperatures ranging from F. to in excess of 1000 F. and as high as 2000 F. During this rapid change in heat content, the feed degrades, forming particles which tend to adhere to the exchanger surface.

The determination of fouling rates by drop in heat transfer coefficients would be very difiicult in units where vaporization occurs. It was decided, therefore, to develop an empirical, semiquantitative rating system for the heat exchange tubes, involving a measurement of the area covered by each type of deposit and a visual estimate of the severity of each deposit.

The deposits formed on the heat exchangers in units herein depend on the nature of the feed stock and the temperature. Both skin temperature and fluid temperature are significant factors. These deposits may range from a yellow-brown gum or light varnish at the cool end of the tube, to heavy coke at the hot end. The type of deposit on each distinguishable area on the tube was rated visually according to the following system:

Following this visual rating, the rating number assigned to each distinguishable area on the tube is squared and multiplied by the average length of that area. These numbers are added to give a total rating number for each test.

This procedure is illustrated in the following example:

Light; Medium Light Heavy Type of Deposit varnish varnish coke coke Rating 2 3 4 6 Inches 4 2 6 1 This rating system emphasizes the quality and quantity of coke formed from the thermal decomposition of the feed stock and at the same time takes into account deposits formed from gums which are already present in the stock or which form during the heating process.

Naphthas and naphtha blends were prefiltered through 5.0 micron Millipore filters. This was necessary since even fine foreign particles tended to clog the control valve.

Feeds were not preaerated and care was taken to eliminate air-naphtha contact. With this approach, gum formation in the drum was minimized, and the naphthas evaluated in the laboratory closely approximated those fed to field units.

The additive compounds and compositions evaluated herein were:

AA widely used, commercial available antifouling agent.

BN,N-bis-salicylidene-1,2-diamino propane.

C--A metal deactivator comprising equal parts ofB, above and a nitrogen-based: corrosion inhibitor dispersed in an aromatic solvent (80% by weightsolvent) Antifouling evaluations with various petroleum stocks are set forth in the following tables.

TABLE 1 Virgin naphtha evaluated in Unit at 600 p.s.i.; liquid velocity, 0.2 it./sec.;

vapor velocity, 49 ft./sec. (9st.)

Coker naphtha evaluated in Unit at 600 p.s.i.; liquid velocity, 0.2 it./sec.; vapor velocity, 57 it./sec. (est.)

Percent Reduction Dosage, Oil Temp, Tube in Tube Additive p.p.m. F. Rating Rating Blank 695-705 46 300 695-710 I 41 12 500 670-715 34 26 1,000 700-705 31. 32 2, 000 690-705 26 45 B 700-710 30 35 25 "690-715 22 52 50 705-705 17 63 100 700-710 12 74 C 50 700-710 37 20 100 710-710 32 31 200 695-720 29 37 300 700-730 24 58 400 695-710 28 40 500 715-725 29 J37 'TABLE 3 (Joker-virgin naphtha'mix (%-75%) evaluated in Unit at 600 psi.; liquid velocity, 0.2 ft./sec.; vapor velocity, 52 it. see. (est.).

Straight run and thermally cracked naphtha mix (80%-20%) evaluated in Unit'at 650 p.s.i.;-liquid velocit(y, (tJ.)2 it./sec.; vapor velocity, 44 it./see.

Percent 7 Reduction Dosage, Oil Temp Tube in Tube Additive p.p.m. F. Rating -Rating TABLE 5 Straight run and thermally'cracked naphtha mix (%-20%), evaluated in Unit at 650 p.s.i.; liquid veloeit(y, t./sec.; vapor velocity, 91 ftJsec.

. es H Straight run and thermally cracked naphtha mix (80%-20%), evaluated in Unit at 650 p.s.i.; liquid velocity, 0.2 ft./sec. H

Percent Reduction Dosage, Oil Temp, Tube in- Tube Additive p.p.m. F. Rating Rating 405-425 11 400-425 10 9 25 410-430 1 9 18 50 410-425 j 8 27 415-420 6 45 B 1 400-425 7 36 2. 5 400-425 6 45 5 "400-430 5 55 10 410-430 5 55 C 5 420-435 7 36 10 415-430 5 55 25 405-435 5 55 I TABLE 7 Straight Run Distillate: at 835p.s.i., liquid velocity of 0.2 it./ see.

Percent I Reduction Dos'age, Oil-Temp, Tube in Tube Additive p.p.m. F. Rating Rating Blank 575-595 10 25 575-600 -10 0 '50 585-625 10 0 1 100 580-615 8 "20 250 585-625 5 50 B 5 580-605 4 '60 10 585-605 T 5 50 25 575-625 -5 50 50 590F605 4 '60 .O 25 595-610 7 790 50 590-600 5 50 100 600-610 4 '60 250 605-615 4 "60 TABLE 8 Cracked Distillatezas above Percent 'Reduction Dosage, 0il-Temp., Tube in-Tube Additive p.p.m. F. Rating Rating Blank 595-620 '24 "50 605 -620 21 13 -100 600-620 22 8 250 600-625 24 0 500 600-615 13 '46 1, 000 600-620 13 46 B 5 600-610 23 6 10 605 610 18 25 25 610-625 8 67 50 605-630 5 '87 100 610-630 5 87 C 5 605-620 -24 0 10 600-625 "23 6 25 600-615 16 33 50 600-610 15 38 100 595-600 ll 54 250 615-640 6 75 560 5 87 TABLE 9 TABLE 14 Filtered Distillate Mix (30% cracked, 70% St. Run): as above Evaluation with crude unit naphtha evaluated as above Percent Percent Re- Reduction Formula, Oil Temp., Tube duction in Dosage, Oil Temp., Tube in Tube Additive p.p.m. F. Rating Tube Rating Additive p.p.m. F. Rating Rating 5 Blank 570-620 18 Blank 585-635 26 100 610-630 17 6 A 10 585-630 26 200 605-610 17 6 25 620-650 8 69 300 600-610 16 10 50 600-640 11 58 C A 25 610-630 11. 3 37 100 600-610 11 58 50 620-640 9. 8 46 250 600-610 11 27 100 605-615 6 67 B 1 600-635 0 65 10 10 610-620 5 81 TABLE 25 600-620 5 81 15 Evaluation of hydro desulfurizer unit charge, evaluated as above.

Percent Re- Formula, Oil Temp., Tube duction in TABLE 10 o Additwe p.p.m. F. Rating Tube Ratin Filtered Distillate MlX (30% cracked, 70% t- R at F. 011 6106 5 25 100 605-6 0 20.0 gg fg 20 200 620-660 15. 0 40 Dosage, Oil Temp, Tube in Tube C 32 8 Additive p.p.m. F. Rating Rating 50 615 635 9 1 64 Blank 730450 36 100 625-645 6. 0 76 10 720-750 28 22 715-755 8 78 50 730-755 11 69 25 100 730-780 19 47 250 770-770 28 22 500 720-750 36 0 TABLE 16 B 2. 5 770-785 7 31 Fouling evaluations with the debutanizer bottoms at 600 p.s.i., oil term 5 765-785 5 36 perature approximately 6 F. 10 780-790 4 89 50 780-785 8 78 Percent 80 780-790 1 67 Formula, Reduction in 150 0-760 11 69 Additive p.p.m. Tube Rating Tube Rating 300 750-775 9. 5 73. 5 C 5 750-780 10 72 Blank 5 10 760-790 8 78 100 20 7 25 745-790 6 83 300 17 2 20 50 750-790 5 86 1, 000 15. 1 30 100 750-790 5 86 B 50 7 6 5 100 4; 3 80 C 300 9. 0 58 TABLE 11 Fouling evaluations with combined hydro desulfurizer charge naphtha. Evaluated at 600 p.s.i., veloclty; of liquid 0.2, t./scc.; of vapor, 43 ft./sec. (est) TABLE 17 Percent Re- Fouling evaluations with splitter bottoms, as above Formula, Oil Temp, Tube duction in Additive p.p.m. F. Rating Tube Rating Pe t Formula, Reduction in Blank 590-610 3. 9 Additive p.p.m. Tube Rating Tube Rating A 50 595-605 28. 7 35 100 590-605 19. 7 55 Blank 27. 3 200 597-602 17. 2 6 A 100 25. 7 6 500 595-610 14. 1 68 300 17. 7 28 1,000 595-600 6. 0 86 1, 000 16. 5 40 O 595-601 19. 5 56 B 25 9, 7 64 100 595-600 16. 0 64 100 4, 3 32 100 595-600 12. 3 72 C 300 8. 9 67 200 595-600 9.0 80 300 595-600 9.3 79 50 500 595-600 7. 1 84 TABLE 18 TAB LE 12 Fouling evaluations with the debutanizer feed as above Evaluations with reformer, visbreaker gasoline evaluated as above.

Percent Percent Re- Formula, Reduction in Formula, Oil Temp, Tube duction in Additive p.p.m. Tube Rating Tube Rating Additive p.p.m. F. Rating Tube Rating Blank 20. 3 Bl k 620-630 34 300 19. 7 3 A 100 615-635 31 9 450 17. 3 15 200 620-640 30 12 1, 000 15. 5 24 500 630-650 26 24 B 50 11. 1 45 1, 000 620-640 24 30 100 9. 4 54 C 100 620-640 24 3 C 300 12. 3 39 l? 13 h d l l t d TABLE 19 v lua ions 'th crude unit atmos eric over ea aso ine eva ua e E a t W as tve g Fouling evaluations with the splitter feed as above Percent Re- Percent Formula, Oil Temp., Tube duction in Formula, Reduction in Additive p.p.m. F. Rating Tube Rating Additive p.p.m. Tube Rating Tube Rating Blank 595-610 19 Blank 1s. 4 100 620-635 17. 7 7 A 300 19. O 0 300 605-625 13 31 500 15. 1 18 500 610-625 11 42 1, 000 13. 9 24 C 50 605-625 11 41 B 50 9. 3 9 100 610-635 9 53 100 4. 1 78 200 605-640 6 68 C 300 10. 1 45 Percent 011 Reduction Telnri Tube in Tube Formula,

Rating Rating p.p.m.

Additive Manganese TABLE 21 Evaluation of the American and Texas straight run naphtha mix in unit at 600 p.s.i.; liquid velocity of 0.2 ft./sec.; vapor velocity of 29 ft./sec. (est) Percent Oil Reduction Dosage, Temp, Tube in Tube Additive ppm. F Rating Rating Blank 590-600 C 100 595-605 1.2 595-605 1. 2+100 595-600 1 2+250 600-605 1.2 600-605 1 2+1, 000 600-605 1. 2 590-600 1. 2+67 600-605 32 35 1. 2+100 605-610 18. 2 63 1. 2+250 600-610 10. 3 79 Manganese 1. 2 600-610 26. 3 Chromium 1. 2 595-600 30. 1 2+100 600-605 13. 2 56 Vanadium 1. 600-610 25. 0

TABLE 22 Evaluation of Additives B and C formulations in Refinery Overhead Test Apparatus Corrosion Rate, m.p.y. at ppm. Temp, Additive pH F. 0 2. 5 5

The coker-virgin-naphtha feed stock (Table 3) had the following metals content:

Metal: P.p.'m. Copper, as Cu 0.1 Iron, as Fe 0.1 Nickel, as Ni 0.1 Manganese, as Mn 0.1 Chromium, as Cr 0.1 Vanadium, as V .1

The reformer feed naphtha feed stock (Table 12) had the following metals content:

Metal: P.p.m. Copper, as Cu 0.10 Iron, as Fe 0.18 Nickel, as Ni 0.1 Manganese, as Mn 0.1 Chromium, as Cr 0.1

Vanadium, as V 0.2

TABLE 23 Fouling evaluations with visbreaker feed; test time, 3 hours; 400-450 p.s.i.; wall temperature, 1,0501,100 F.; oil temperature, 860-890 F.;

flow rate, 1.1 ft./sec.; heat input, 11,500 B.t.u./hr.-sq. it.

Tube Rating Percent Additive P.p.n1. Total Reduction Blank 541 A 3, 000 428 21 5, 000 382 20 3, 000 257 52 As shown in the foregoing tables, naphtha (Tables 1-6, 11, 14, 20 and 21) have severe deposit problems as evidenced by the tube ratings for the blanks at oil (naphtha) temperatures above 495 F. and especially above 590 F. Lesser deposit problems occur at lower temperatures of the order of 405-425 F. (Table 6). Reformer, visbrcaker gasoline, the hydrodesulfurizer unit charges, debutanizer bottoms, and splitter bottoms and atmospheric overhead gasoline are distillates in the naphtha class (Tables 12, 13 and 15-17). Splitter feeds Table 19) contain naphthas and lighter fractions. The straight run distillate, cracked distillate, and distillate mix (Tables 7-10) have more severe deposit problems wherein the oil contains cracked distillate (Table 7 vs. Tables 8-10) at oil (distillates (temperatures of 575 F. and above. Such distillates are defined in the petroleum art as fractions heavier than naphthas and lighter than gas oils. Visbreaker feeds (Table 23) are primary crude oils and show severe deposit problems as evidenced by the blank rating. Debutanizer feed (Table 18) contains butane and heavier fractions at oil (debutanizer feed) temperatures of at least about 600 F. (fouling evaluations with the debutanizer bottoms at 600 p.s.i., oil temperature approximately 600 F., heading of Table 16).

The invention is hereby claimed as follows:

1. In a process wherein a petroleum fraction stock in the naphtha to gas oil class is subjected to direct contact with hot, metal, heat transfer surfaces hot enough to elevate the temperature of said stock to at least 495 F., the improvement comprising inhibiting the formation from chemicals in said stock on said hot heat transfer surfaces of deposits which are organic and/or inorganic in nature and are primarily polymerization products converted at said elevated temperatures to coke-like deposits by incorporation into said stock prior to the elevation of the temperature thereof of a composition consisting essentially of as the active essential ingredient thereof one to 500 parts per million of a metal deactivating compound of the formula wherein R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a ring carbon atom ortho to the N=CH group, and R represents a group of the class consisting of aromatic groups, cycloaliphatic groups containing 6 carbon atoms in the ring, heterocyclic groups containing hetcrocyclic rings, of 6 atoms, the hetero atom being nitrogen, and in which the two N atoms are attached directly to adjacent ring carbon atoms or to the most closely positioned ring carbon atoms of different rings other than carbon atoms forming part of the linkage between the two rings of the R group, and an aliphatic radical having the two N atoms attached directly to different carbon atoms of the same open chain of R.

2. A process as claimed in claim 1, wherein said metal deactivating compound is a metal complexing compound for a metal selected from the group consisting of copper, chromium, nickel, iron and manganese.

3. A process as claimed in claim 1, wherein said temperature is at least 590 F.

4. A process as claimed in claim 1, wherein said metal deactivating compound is a compound of the formula wherein R is a 1,2-alkylene, saturated hydrocarbon group having a total of 2-18 carbons.

5. A process as claimed in claim 4, wherein said compound is N,N-bis-salicylidene-ethylene diamine.

6. A process as claimed in claim 4, wherein said compound is N,N-bis-salicylidene-1,2-propane diamine.

7. In a process wherein a crude oil is subjected to direct heat exchange with hot, metal, heat exchange surfaces having surface temperatures of in the range of about 100 F. to 2000 F. to heat said crude oil to a processing temperature, the improvement comprising inhibiting the formation of coke-like deposits on said surfaces by incorporation into said crude oil prior to contact with said hot surfaces of a composition consisting essentially of as the active essential ingredient thereof one to 500 parts per million of a metal deactivating compound of the formula wherein R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a ring carbon atom ortho to the N=CH group, and R represents a group of the class consisting of aromatic groups, cycloaliphatic groups containing 6 carbon atoms in the ring, heterocyclic groups containing heterocyclic rings of 6 atoms, the hetero atom being nitrogen, and in which the two N atoms are attached directly to adjacent ring carbon atoms or to the most closely positioned ring carbon atoms of different rings other than carbon atoms forming part of the linkage between the two rings of the R group, and an aliphatic radical having the two N atoms attached directly to diiferent carbon atoms of the same open chain of R.

8. A process as claimed in claim 7, wherein said metal deactivating compound is a metal complexing compound for a metal selected from the group consisting of copper, chromium, nickel, iron and manganese.

9. A process as claimed in claim 7, wherein said metal deactivating compound is a compound of the formula OH HO wherein R is a 1,2-alkylene, saturated hydrocarbon group having a total of 2-18 carbons.

10. A process as claimed in claim 9, wherein said compound is N,N-bis-salicylidene-ethylene diamine.

11. A process as claimed in claim 9, wherein said compound is N,N-bis-salicy1idene-1,2-propane diamine.

12. In the processing of composition containing a normally gaseous hydrocarbon having a boiling point in the range of 250 F. to 100 F. wherein the gaseous hydrocarbon in a liquified state at elevated temperature and elevated pressure, the improvement comprising inhibiting the formation of organic and inorganic fouling deposits on surfaces in contact therewith with temperatures of said surfaces between 200 F. and 2000 F. by incorporation into said normally gaseous hydrocarbon, a composition consisting essentially of as the active essential ingredient thereof one to 500 parts per million of a metal deactivating compound of the formula wherein R represents a member of the group consisting of aromatic rings and unsaturated heterocyclic rings of 5 to 6 atoms in which the hetero atom is nitrogen, the OH radical being attached directly to a ring carbon atom ortho to the N=CH group, and R represents a group of the class consisting of aromatic groups, ycloaliphatic groups containing 6 carbon atoms in the ring, heterocyclic groups containing heterocyclic rings of 6 atoms, the hetero atom being nitrogen, and in which the two N atoms are attached directly to adjacent ring carbon atoms or to the most closely positioned ring carbon atoms of dilferent rings other than carbon atoms forming part of the linkage between the two rings of the R group, and an aliphatic radical having the two N atoms attached directly to different carbon atoms of the same open chain of R.

13. A process as claimed in claim 12 wherein said metal deactivating compound is a metal complexing compound for a metal selected from the group consisting of copper, chromium, nickel, iron and manganese.

14. A process as claimed in claim 12, wherein said metal deactivating compound is a compound of the formula OH HO wherein R is a 1,2-alkylene, saturated hydrocarbon group having a total of 218 carbons.

15. A process as claimed in claim 14, wherein said compound is N,N-bis-salicylidene-1,2-propane diamine.

16. A process as claimed in claim 14, wherein said compound is N,N'-bis-salicylidene-ethylene diamine.

References Cited UNITED STATES PATENTS Re. 26,330 1/1968 Colfer 20848 2,181,121 11/1939 Downing et al 2325() 2,908,624 10/1959 Johnson et al. 208-48 2,928,876 3/1960 Spivak et al. 260566 2,962,442 11/1960 Andress 252--51.5 3,054,824 9/1962 Arrigo 260566 3,017,343 1/ 1962 Pollitzer 20847 3,155,463 11/1964 Andress et al 4462 3,224,957 12/1965 Kent 20848 3,328,283 6/1967 Godar 208-48 3,328,285 6/1967 Godar 20848 3,034,876 5/1962 Gee et a1 4462 3,068,083 12/1962 Gee et al. 4470 3,390,073 6/1968 Godar et al 20848 3,437,583 4/1969 Gonzalez 20848 3,442,791 5/1969' Gonzalez 20848 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner US. Cl. X.R. 4473 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5,49 l2l9 Dat Jagugrv 2?. 1970 Inventor) Richard M. Miller It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column line 47, "oxiation" should read --oxidation--.

Column 5, line 47, "polymeric surfaces" should read --po1ymeric substances are thermoplastic and may stick to the hot metal surfaces--.

Column 12, Table 7, in the last column "20" should read "30"; Table 8, in the last column, above "1}" insert "6".

Column 13, line 39, Table 11, "veloclty" should read --velocity--.

Column 16, line 12, "naphtha" should read --naphthas--; line 21, "table" should read --Table--; line 26, "(distillates should read disti1lates)--.

SIGNED RND SEALED JUN 3 01970 .J Am

EdwardRFletchu-Jr. WILLIAM E W m Attesting Officer commissioner of rab alfil 

